Three foot six inch gauge railways
Railways with a track gauge of 3 ft 6 in/1,067 mm were first constructed as horse-drawn wagonways. From the mid-nineteenth century, the 3 ft 6 in gauge became widespread in the British Empire, and was adopted as a standard in Japan.
There are approximately 112,000 kilometres (70,000 mi) of 1,067 mm gauge track in the world.
In Sweden, the gauge was nicknamed Blekinge gauge, as most of the railways in the province of Blekinge had this gauge.
An alternate name for this gauge, Cape gauge, is named after the Cape Colony in what is now South Africa, which adopted it in 1873. The term Cape Gauge is used in other languages, such as the Dutch kaapspoor, German Kapspur, Norwegian kappspor and French voie cape. After metrication in the 1960s, the gauge was referred to in official South African Railways publications as 1065 mm instead of 1067 mm.
The gauge is sometimes referred to as CAP gauge, after C.A. Pihl.
The gauge name Colonial Gauge was used in New Zealand.
In Australia the imperial (pre-metric) term 3 foot 6 inch is used. In some Australian publications the term medium gauge is also used, while in Australian states where 4 ft 8 1⁄2 in (1,435 mm) is the norm, 1,067 mm (3 ft 6 in) gauge is often referred to as narrow gauge.
In Japan 1,067 mm (3 ft 6 in) gauge is referred to as kyōki (狭軌), which directly translates as narrow gauge. It is defined in metric units.
Similar rail gauges in respect of aspects such as cost of construction, practical minimum radius curves and the maximum physical dimensions of are:
...
Wikipedia